A downdraw method has conventionally been used as one method of manufacturing a glass sheet. In the downdraw method, split flows of molten glass which overflows from a forming body is created so that the molten glass flows down along the surface of the forming body. The two streams of molten glass are then merged at the lower end of the forming body to form a glass sheet. The glass sheet thus formed is annealed while being conveyed downward. In the annealing process, the glass sheet transitions from a viscous stage to an elastic stage via a viscoelastic stage.